Preparation and Characterization of Coal-Pitch-Based Needle Coke (Part III): The Effects of Quinoline Insoluble in Coal Tar Pitch

High-temperature coal tar pitch is often used to produce high-quality needle coke. Its basic properties [such as fa value, β resin, and quinoline insoluble (QI) content] significantly affect the quality of the resulting needle coke. Refined pitch with fa and β-resin values in the 0.95–0.98 and 13–16% ranges, respectively, is considered an excellent raw material for this purpose. The influence of QI content on the characteristics of coal-based needle coke is still not fully clarified in the literature. To analyze how QI content affects coal-based needle coke properties, this work used 10 different kinds of coal tar pitch (refined from the same source) with different QI contents for the needle coke production. We thoroughly analyzed optical microstructure and crystalline sizes, surface morphology and microstrength, true density, and coefficient of thermal expansion (CTE) of the resulting products. The high-temperature coal tar pitch with the QI content of <0.8% was a preferable raw material to obtain superior needle coke; it possessed higher density and microstrength, lower CTE, and graphitized more easily than cokes with other parameters.